probably because it is a weapons and could either put someone in a comma or crush them or kill them and you pretty much answered your own question because anything that can be used as a weapon (which you said in the question) is illegal.
Illegal weapons are by definition already banned.
No, uranium itself is not illegal to possess, but it is highly regulated due to its radioactive properties and potential use in nuclear weapons. Unauthorized possession and use of uranium can result in legal consequences.
if one of the public make nuclear weapons of course they can use but it can then become illegal if they harm someone
No. There is an existing Federal restriction on importing the weapons, but registered weapons are still legal to own and use.
None. Don't steal horses. It's illegal.
It depends on your living area. In fact, very few weapons are actually illegal. It's just usually illegal to carry concealed weapons. If you live in Canada were there is no right to bear arms, only then is it illegal. If you have the right to bear arms then no it is not illegal.
Answers.com does not provide instructions for making illegal weapons.
gun trafficing is illegal. transporting for sale of illegal weapons.
In many countries they are considered offensive weapons and are illegal.
No.
No because it is illegal to hurt people with knives but if you use a knife as a weapon to kill, you can be thrown in jail for years.
No, both are legal weapons for nations to use in war. Only chemical and biological weapons are prohibited by international law (although that has not stopped certain countries from using them).