Basically the issue with the knees is you don't want to start riding a horse too strenuously until the knees close. For each breed it is different. Some close at 3, others, like drafts and WBs, can wait until 5 or so.
the act of making or enacting laws. 2. a law or a body of laws enacted. Origin of legislation.
Legislation is that source of law which consists in the declaration of legal rules by a competent authority. Legislature is the direct source of law. Legislature frames new laws, amends the old laws and cancels existing laws in all countries. In modern times this is the most important source of law making.