A good thesis for a paper on gun control would be: "Gun laws are the cause of much of the violent crime in the United States and need to be changed in order to make it easier for Americans to purchase handguns, carry them as concealed weapons and protect themselves." For those people with the opposite approach to gun control, a good thesis for the paper would be: "Gun laws are the cause of much violent crime in America and need to be changed so that it is difficult to obtain guns and a person owning an illegal firearm will find himself with a stiff prison sentence even as a first-time offender."
Thesis statements must be concise and must act as a road map for the paper. They should let the reader know what to expect from reading the rest of the paper and should also tell the reader how the paper intends to interpret the subject matter, such as gun control, of the paper. A persuasive paper will also need to make a claim and the claim should be controversial enough that other might dispute it.