OK - you clearly do not understand the law or choose to interpret it in such a way it works to your advantage.
By your own quote (emphasis added)
Harmful interference" means interference which endangers the operation of a radio navigation service or other safety radio service or otherwise seriously impairs, impedes or repeatedly interrupts the operation of a radio service which operates in accordance with the applicable provisions of international, Community or national law.
Perhaps you could explain to me what a Radio/GPS jammer exactly does if it isn't imparing, impeding or interrupting the operation of a radio service which is operating under law/license.
In fact - a jammer is specifically designed to cause disruption and/or block reception of these signals in its operating envelope.
So no - they are not legal to use in your country which comes under European telecommunications treaties.
I have stated above, in some countries they are perfectly legal to sell and own but NOT to operate!
Understand your local and countries laws.
However - this is moot since we are talking about a GPS anomaly within the United States which without question has radio spectrums allocated, governed and enforced by the FCC and the use of jamming or interrupting devices in the USA is most definitely illegal.