Last I checked, there was a legislative process that is overseen by elected officials required to change most laws around marriage. You have to sign a contract with the state to get a license and operate a vehicle legally, I don't see people up in arms and refusing to drive because the state can change driving rules. Same with incorporating a company in any given state. You are subject to that state's laws even if they change after you start your company, but you take that risk because you determined that the protections you get from signing that contract is more valuable than the risk from not doing so.
Also, other than legalizing no-fault divorce and expanding marriage to same-sex couples, what are the changes that states could make which are so scary to you? Sharing wealth 50/50 in the case of divorce is not some new thing.