The FBI is part of DOJ, which is an executive branch department under Biden's direct authority. If he thinks it's "simply wrong", he can just order them not to do it. He's not limited to "criticizing" it.
> “Going forward, consistent with the President’s direction, this Department of Justice – in a change to its longstanding practice – will not seek compulsory legal process in leak investigations to obtain source information from members of the news media doing their jobs,” Anthony Coley, Justice Department spokesman, said in a statement.
They are changing a "practice".
One uses laws to prevent practices one does not like, not "directions".
If you want a law to prevent this I'm not sure why you're criticizing Biden. He is the President, no the Legislature.
If you think there should be a law, then your complaint should be for congress.