Since it obviously hasn't sunk in for you yet, let me try to simplify it for you further.
"Newton's laws governing motion" is plural.
"Newton's Laws of Motion" is singular. Notice the difference? The latter is all capitalized because it is a title given to the collective laws known as
"Newton's Laws of Motion", and titles are singular. Just like
"The Grapes of Wrath" or
"Adventures of Huckleberry Finn" are singular.
Or to put it into terms which you might relate to better:
Is it grammatically correct to ask -
"Has BMW's M-series improved over the years?" Yes, it is, even though the M-series consists of several different cars (M3, M5, M6), but they are collectively known as the
"M-series", so
"M-series" is singular. Likewise, although
"Newton's Laws of Motion" consists of several different laws (1st, 2nd, 3rd), they are collectively known as
"Newton's Laws of Motion", which is singular.
If you had paid attention in grammar school, you would have known that.