A few people have made proposals, though nothing has been taken seriously. The first one was a NY state proposal that never got out of committee. The second is

A few people have made proposals, though nothing has been taken seriously. The first one was a NY state proposal that never got out of committee. The second is weird. It seems to be a draft of a bill, I don't know if they actually proposed this in committee. And it's odd. It requires that companies must provide data to law enforcement with a valid court order. Which is redundant: of course if law enforcement has a court order for a company to provide data they have to provide it, unless they can contest the court order. The uses the phrase "make data intelligible" which reading further seems to mean you have to decrypt the data. So it looks like it's meant to require companies to be able to decrypt any of their secure systems with a valid court order, hence requiring a backdoor. But Section 3.(b) says "Nothing in this Act may be construed to authorize any government officer to require or prohibit any specific design or operating system to be adopted by any covered entity." That seems to clearly state this Act can't require a company to put a backdoor in their system. It's really an odd little document.