Of course, even if it's banned, you can buy it online at shopping. GPS jammer used to steal cars can also be purchased online.
If you have a GPS system installed, if you think it can be retrieved even if it's stolen, that's not good. Thieves know this too. They can use the GPS jammer to jam the tracking system.
Once the thief steals your car with a GPS jammer, I can't get it back. However, this cannot be solved completely. The thief decided to remove the GPS system by moving the stolen vehicle to a secret location. It's impossible to track stolen vehicles. This is why the government prohibits jamming devices.
In fact, cell phone jammers can be used in many countries, but GPS jammers can't be used. When you think about it, there are obviously many ways you can use a GPS jammer to do bad things. In an online store, you can buy a GPS jammer regardless of your intentions. If you notice that the in-car signal is stopped while driving, you may want someone to use the jammer next to you.