The answer is in your thread title. It's no use looking for more details here, because those depend on what country you live in. If you are lucky there will be a dot gov (or equivalent) www site where you can pick up some preliminary information.

You can put up some speed bumps but in the end they can always be copied if someone wants too.

For example you use the the image as a background image in a container. Then you use transparent .gif and stretch it out to the size of the background image. When someone right clicks and "Saves image" they save the transparent image.

It's a gimmick as anything else will be and will only slow down the average people.