A quicker way is to note that a given policy would be difficult to effectively enforce. People like to say unenforceable, which is rarely true given enough resources. But if there are two solutions to an issue, and one isn't as easy to enforce, that is a valid point. Using gun control as an example, restricting sale of ammunition instead of firearms might be difficult to enforce, because ammunition is easier to manufacture at home. Restricting sale of marijuana isn't effective because anyone can grow it in a closet, but testing at employment centers adds a lot more friction as you say, and you don't neednto monitor people's power usage or send around sniffer trucks.
