comment: I've used a somewhat innocuous abstraction of 'pranks in space' below, but there's no end to the trouble that could be caused and the increasing ease with which a state (nation or otherwise) could cause it. The scope of Article IX of The Outer Space Treaty of 1967 is pretty narrow - what exactly happens if party A says that party B may be in violation of article IX? Is there a board of arbitration? Are there any mechanisms of 'punishment' established? What about a non-signatory state? Misdeeds on earth are getting easier to detect and report by independent news media, but how many news orgs have NORAD's capability?
The discussion in the recent article in The Conversation: SpaceX explosion shows why we must slow down private space exploration until we rewrite law focuses mostly on accident and liability issues, and points out that the 50 year old Outer Space Treaty ratified in 1967 may need to be dusted off and looked at more closely. I'd recommend reading the full article - here is a paragraph near the end:
With the increase in private participation in space experimentation and perhaps even mineral mining, the provisions governing civil liability over mishaps arising from the operations of a space station are likely to become one of the most contested areas of space law. What if a module or component part fails to function on a space station? In the absence of multilateral rules on this point, a patchwork of legal rules is gradually maintained through MOUs (Memorandum of Understanding) and other national laws such as the US Commercial Space Launchings Act (CSLA) of 1978. How will private companies fit into these as they possibly become partners?
Further, the "PrankSat" situations may multiply when it becomes more and more common to add significant propulsion capability to cubesats, and control may not be under the same number of levels of security that is currently used for "serious" satellites.
Other terms that may apply in some cases include "tit for tat-sat" and "a proportional response-sat."
above: Outer Space Treaty parties, signatories, and non-signatories as of March 2015 from here, modified by pasting legend (sorry Antarctica).
If a hypothetical President Wisenheimer felt secure that his/her country's large supply of neodymium, palladium and unobtainium gives them some economic protection, what international regulations, agreements, or other forces could help the rest of the world stop, or at least discourage the president from allowing his/her brother in law's aerospace company OrbitalPranksters from launching PrankSat and putting it in orbit in front of the Hubble Space Telescope?
The pranksters know what a collimator is, and understand that the basic point-to-parallel-to-point method will add to the image on the CCD even if it significantly under-fills the telescope's aperture. It will be in focus at all distances since both have infinity conjugate focci. (image from a randomly chosen internet optics catalog), and here are some other collimators that project images into telescopes.
PrankSat could navigate near the HST, or - since the divergence of the FOV is small - intercept the scheduled HST view from kilometers away and "Flash". It could also attach itself to the HST in some way, occasionally move into view, and really become a pest.
above: I found this on the internet. Used with warm regards to Dr. Tyson and all he does to further the public's understanding of science.