I'm not sure what you mean by "winner takes all laws." We essentially have that now since almost all electors vote for their party's presidential candidate.
You may be talking about the popular vote interstate compact. It says states will give all their electoral votes to the candidate who wins the national popular vote. It will not take effect until enough states are part of the compact that have over 270 electoral votes. States not part of the compact do not have to do this, of course, but it won't matter if those states with 270+ electoral votes agree. Currently 15 states with 196 electoral votes are part of the pact.