Can law enforcement search the content of a person’s safe deposit box in the bank?
With the appropriate search warrant, yes.
As Monty said, with the appropriate warrants, yes, it can be searched.
Unless, of course, you happen to be very close to said box (within arm’s reach, in fact) when you are arrested, it can be searched without a warrant, based on the need to keep the arresting officers safe(wingspread search).
Other than that, they need a warrant. You have a reasonable expectation of privacy in a safe deposit box.
Anyone who says they don’t like children obviously isn’t cooking them properly.