# Could Canada blockade the St. Lawrence River and what would happen if they did so? **URL:** \ **Category:** In My Humble Opinion\ **Created:** [March 7, 2025, 6:37am UTC](https://boards.straightdope.com/t/could-canada-blockade-the-st-lawrence-river-and-what-would-happen-if-they-did-so/1015234 "2025-03-07T06:37:07Z")\ **Posts on this page:** 14\ **Page:** 1
**Author:** ![X.L.Lent](https://avatars.discourse-cdn.com/v4/letter/x/a5b964/32.png) [@X.L.Lent](https://boards.straightdope.com/u/X.L.Lent)\ **Post date:** [March 7, 2025, 6:37am UTC](https://boards.straightdope.com/t/could-canada-blockade-the-st-lawrence-river-and-what-would-happen-if-they-did-so/1015234/1 "2025-03-07T06:37:07Z")
There unfortunately has been some friction between the USA and Canada lately. As an American I am embarrassed by this and would like to apologize for the actions of the idiots that currenly occupy the top positions in our government. My question is: could Canada retaliate by blocking the Saint Lawrence River and prevent ships from going to ports on the American side of the Great Lakes? Could Canada stop ships bound for USA ports from using the Welland Canal? (The Welland Canal allows ships to bypass Niagara Falls and it’s on the Canadian side of the border). What would be the imact of such a blockade? Would it be considered and act of war? _Mods: if you want to move this question to the Politics & Elections forum that is OK with me._ ---
**Author:** ![Snarky\_Kong](https://avatars.discourse-cdn.com/v4/letter/s/a183cd/32.png) [@Snarky\_Kong](https://boards.straightdope.com/u/Snarky_Kong)\ **Post date:** [March 7, 2025, 6:46am UTC](https://boards.straightdope.com/t/could-canada-blockade-the-st-lawrence-river-and-what-would-happen-if-they-did-so/1015234/2 "2025-03-07T06:46:09Z")
That’s an act of war and I suspect the US would respond to it as such. ---
**Author:** ![Cervaise](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cervaise/32/16693_2.png) [@Cervaise](https://boards.straightdope.com/u/Cervaise)\ **Post date:** [March 7, 2025, 6:57am UTC](https://boards.straightdope.com/t/could-canada-blockade-the-st-lawrence-river-and-what-would-happen-if-they-did-so/1015234/3 "2025-03-07T06:57:28Z")
Agree that a full blockade would be an act of war. There are, however, smaller intermediate steps that would fall short of such a declaration yet allow Canada to flex its muscles a bit. Random “inspections” of cargo ships along the way, for example, to ensure nobody’s trying to defeat border controls or smuggle American armaments into Canada via mid-route offloading. That would slow things down and create painful pressure while still being superficially “justified” in the current political context. ---
**Author:** ![dolphinboy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dolphinboy/32/330_2.png) [@dolphinboy](https://boards.straightdope.com/u/dolphinboy)\ **Post date:** [March 7, 2025, 1:00pm UTC](https://boards.straightdope.com/t/could-canada-blockade-the-st-lawrence-river-and-what-would-happen-if-they-did-so/1015234/4 "2025-03-07T13:00:28Z")
Whether an act of war or not, the US military would clear any obstacles Canada used to block passage of our ships on the river. I think it would lead to a skirmish, but not necessarily full out war, which undoubtedly Canada would lose . ---
**Author:** ![Spiderman](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/spiderman/32/230_2.png) [@Spiderman](https://boards.straightdope.com/u/Spiderman)\ **Post date:** [March 7, 2025, 2:48pm UTC](https://boards.straightdope.com/t/could-canada-blockade-the-st-lawrence-river-and-what-would-happen-if-they-did-so/1015234/5 "2025-03-07T14:48:10Z")
Admittedly I don’t know much about maritime law but doesn’t the St. Lawrence go deep into Canada, past Montreal & Quebec cities? Do they have rights to exclude who goes into their rivers the same way there are fishing boundaries for 12(?) miles offshore? Could a Russian ship come right up the Potomac or Chesapeake to deliver _one_ container in Washington or Baltimore? ---
**Author:** ![Elmer\_J.Fudd](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/elmer_j.fudd/32/1211_2.png) [@Elmer\_J.Fudd](https://boards.straightdope.com/u/Elmer_J.Fudd)\ **Post date:** [March 7, 2025, 3:02pm UTC](https://boards.straightdope.com/t/could-canada-blockade-the-st-lawrence-river-and-what-would-happen-if-they-did-so/1015234/6 "2025-03-07T15:02:32Z")
There is nothing Canada or any other country could do that would be more disruptive to the day to day importation of goods into the United States than what Trump, himself, is already doing. ---
**Author:** ![Pork\_Rind](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pork_rind/32/111_2.png) [@Pork\_Rind](https://boards.straightdope.com/u/Pork_Rind)\ **Post date:** [March 7, 2025, 3:12pm UTC](https://boards.straightdope.com/t/could-canada-blockade-the-st-lawrence-river-and-what-would-happen-if-they-did-so/1015234/7 "2025-03-07T15:12:39Z")
Yeah, what’s line? “Don’t interrupt your enemy when he’s making a mistake.” ---
**Author:** ![X.L.Lent](https://avatars.discourse-cdn.com/v4/letter/x/a5b964/32.png) [@X.L.Lent](https://boards.straightdope.com/u/X.L.Lent)\ **Post date:** [March 7, 2025, 4:11pm UTC](https://boards.straightdope.com/t/could-canada-blockade-the-st-lawrence-river-and-what-would-happen-if-they-did-so/1015234/8 "2025-03-07T16:11:52Z")
So it would be an act of war even though the blockade is taking place inside Canadian territory? Are the St. Lawrence and Welland Canal considered to be Canadan or international waters? ---
**Author:** ![rsat3acr](https://avatars.discourse-cdn.com/v4/letter/r/a3d4f5/32.png) [@rsat3acr](https://boards.straightdope.com/u/rsat3acr)\ **Post date:** [March 7, 2025, 9:22pm UTC](https://boards.straightdope.com/t/could-canada-blockade-the-st-lawrence-river-and-what-would-happen-if-they-did-so/1015234/9 "2025-03-07T21:22:38Z")
I guess they could stop every ship and go over it with a fine toothed comb looking for fentanyl. Trump couldn’t say much since part of the reason for the tariffs was drugs manufactured in China and smuggled in through Canada and Mexico. ---
**Author:** ![Pleonast](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pleonast/32/1183_2.png) [@Pleonast](https://boards.straightdope.com/u/Pleonast)\ **Post date:** [March 7, 2025, 9:36pm UTC](https://boards.straightdope.com/t/could-canada-blockade-the-st-lawrence-river-and-what-would-happen-if-they-did-so/1015234/10 "2025-03-07T21:36:55Z")
> [@Snarky\_Kong](#): > > That’s an act of war and I suspect the US would respond to it as such. The U.S. might respond that way, but there are parts of the seaway that are entirely within Canada. Canada has inherent sovereignty there. The U.S. and Canada have treaties governing access, but we’ve already seen how much the U.S. regime values those. > [@rsat3acr](#): > > I guess they could stop every ship and go over it with a fine toothed comb looking for fentanyl. This would be a more effective protest than directly blockading the seaway. Every southbound vessel with a U.S. destination gets to be thoroughly inspected for illegal cargo and the privilege of paying for the inspection. ---
**Author:** ![Dag\_Otto](https://avatars.discourse-cdn.com/v4/letter/d/439d5e/32.png) [@Dag\_Otto](https://boards.straightdope.com/u/Dag_Otto)\ **Post date:** [March 7, 2025, 9:57pm UTC](https://boards.straightdope.com/t/could-canada-blockade-the-st-lawrence-river-and-what-would-happen-if-they-did-so/1015234/11 "2025-03-07T21:57:59Z")
> [@rsat3acr](#): > > I guess they could stop every ship and go over it with a fine toothed comb looking for fentanyl. Trump couldn’t say much since part of the reason for the tariffs was drugs manufactured in China and smuggled in through Canada and Mexico. I like this idea. And if any fentanyl is found perhaps the ship could be seized. Alternatively, since this is a trade war, maybe a tariff could be levied based on the value of the cargo that passes through Canadian territory. ---
**Author:** ![Robot\_Arm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robot_arm/32/18280_2.png) [@Robot\_Arm](https://boards.straightdope.com/u/Robot_Arm)\ **Post date:** [March 7, 2025, 10:52pm UTC](https://boards.straightdope.com/t/could-canada-blockade-the-st-lawrence-river-and-what-would-happen-if-they-did-so/1015234/12 "2025-03-07T22:52:03Z")
> [@Dag\_Otto](#): > > Alternatively, since this is a trade war, maybe a tariff could be levied based on the value of the cargo that passes through Canadian territory. When Trump imposed tariffs on hoods from Canada, then almost instantly granted a one month exemption for American car companies, I thought the Canadian PM should have imposed a 25% export tariff on any car parts being shipped into the U.S., effective only as long as the exemption os in place. Call Trump’s bluff; quit dancing to his tune and make him dance to yours. ---
**Author:** ![Northern\_Piper](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/northern_piper/32/5304_2.png) [@Northern\_Piper](https://boards.straightdope.com/u/Northern_Piper)\ **Post date:** [March 8, 2025, 3:32am UTC](https://boards.straightdope.com/t/could-canada-blockade-the-st-lawrence-river-and-what-would-happen-if-they-did-so/1015234/13 "2025-03-08T03:32:23Z")
> [@Snarky\_Kong](#): > > That’s an act of war and I suspect the US would respond to it as such. Why? The estuary of the St. Lawrence is entirely Canadian domestic waters. Not that Trump would need a legal excuse. > **[St. Lawrence River](https://en.wikipedia.org/wiki/St._Lawrence_River)** > > The St. Lawrence River (French: Fleuve Saint-Laurent, .mw-parser-output .IPA-label-small{font-size:85%}.mw-parser-output .references .IPA-label-small,.mw-parser-output .infobox .IPA-label-small,.mw-parser-output .navbox .IPA-label-small{font-size:100%}pronounced \[flœv sɛ̃ lɔʁɑ̃\]) is a large international river in the middle latitudes of North America connecting the Great Lakes to the North Atlantic Ocean. Its waters flow in a northeasterly direction from Lake Ontario to the Gulf of St. Lawrence... ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [March 8, 2025, 5:02am UTC](https://boards.straightdope.com/t/could-canada-blockade-the-st-lawrence-river-and-what-would-happen-if-they-did-so/1015234/14 "2025-03-08T05:02:41Z")
> [@Northern\_Piper](#): > > Why? Because it would be an act designed to economically harm America…and because the only national sovereignty the US has ever been concerned with is its own. America has the right to decide what Canada does on its own territory because it’s America, and Canada isn’t. That was its attitude even _before_ Trump.