In a contract, should exceptions be stated to a clause if they're required by law?

Question

Should a clause state possible exceptions to make it clear they will comply with the law? For example "no animals in the building" may be seen as discrimination against people with guide dogs, so should it contain an exception and say "no animals in the building except for service animals?

Another one may be medical marijuana. If a contract states "employees may not be in possession or under the effects of drugs at work", should it add "unless prescribed by a doctor"? If they don't add this could the people who wrote the contract be sued?

Answer 1

A contract should cover the contingencies that you think of and make provision for the ones that you don't.

As noted in Is it necessary to state in a contract that if one part is found unenforceable, the rest still is? a void provision may make the entire contract void. This is why contracts often deal with conflicts with the law explicitly: "To the extent permitted by law ..."

Of course, this only matters if the parties go to court: if they handle the discrepancies and contingencies in a way that avoids a dispute escalating to that level it isn't a problem, is it?