* Clarity: "Laws that govern" clearly states that the laws are the ones responsible for controlling or regulating something.
* Grammar: "The which governs" is grammatically incorrect. "Which" should be used to refer back to a noun already mentioned, and "the" is unnecessary in this context.
Here are some examples of how you can use "laws that govern":
* "The laws that govern immigration are complex and constantly changing."
* "The laws that govern the use of social media are being debated."
While you could technically say "laws which govern," it's less common and may sound slightly awkward.