If you are unable to get a court to test the proportionality of a system, or to verify that the system or practice is necessary in a democratic society, i.e. that there are no less invasive means to achieving the stated goals, then one strategy is to present your own alternative.
This was our strategy in the UK. We felt that it was unlikely that we could ever defeat the ID card initiative if we didn't have some idea of what could be a reasonable alternative. After consultation with experts on the problems with the Government's proposed solution, we proposed a decentralised and distributed solution. This of course raised the ire of the Government but did promote a useful debate on costs and feasibilities. One survey done by the Open University found that the public was more supportive of our alternative ID system than the Government's. This could go some way in alleviating the concerns of the public who are in fact pro-ID card, but not certain about the Government's ability to develop one.
A similar approach was used by a coalition of industry and civil society in the Ukraine. When the Government proposed a policy on retention, the coalition proposed an alternative regime that still involved retention, but just of a different form. This alternative proved to be distraction enough so that the Government's proposal failed and was forced to start over again with a less invasive proposal.
Of course alternatives are dangerous because sometimes they can be adopted, and we must all be weary of such strategies emerging from civil society and even regulators lest they be adopted when the true strategy is to defeat the principle.