There is a rumor around that a former member of Scientology could be declared "Fair Game", meaning that illegal actions could be taken against this person with Church officials closing both eyes. This is nonsense and has no evidence at all.
A policy of "Fair Game" does not exist within the Church. There was an early policy called "Fair Game" that was cancelled in 1968. The purpose of that policy was to make it known that a person who has left the Church was no longer entitled to the privileges of membership. L. Ron Hubbard himself testified on this in 1976 (link below), making clear that nothing of this meant to violate the law. And that did not happen either.
Scientology critics sometime interpret any lawful action the Church takes to defend itself against their claims or treatment as "harassment" and "Fair Game". The Church does use the same legal tools that anybody else can use, such as lawful information gathering and evidence collection, to defend themselves from unfounded suits, to enforce a legal right or to guard against infiltration and sabotage. This is so common amongst religious organizations as to be routine.
The Church is also within its rights to question the motives of people who would seek to destroy it and to defend itself with lawful means. Other religions also question the motives of those who would seek to destroy them, as well as taking lawful measures to protect themselves, as these examples illustrate.
Basically, Scientology defends itself from attack, by legal means. Just like any other religion would do.
And the misinterpreted policy of "Fair Game"? It is used as an attack method by apostates and hatemongers. It is not a policy used by the Church, it was cancelled 40 years ago. And when it was used, it was not used as is alleged.
Event adamant critics of the Church of Scientology have testified to that. For example, in a most interesting set of declarations an ex-Scientologist said:
"...it has become a routine practice of litigants to make accusations against the Church, including even false allegations of threats of murder, which would be summarily thrown out of court as unsupported and scandalous in other litigation. They do it because it works, and they do it by deliberately mischaracterizing the term "Fair Came". They do it as an intentional means to destroy the reputation of the Church in the context of litigation so that they can win money or force the Church to settle."
"The term "fair game" has become a catch phrase for those who attack the Church. When I was in the Church I never heard it referred to as a policy to be used, the only time it was discussed was in reference to litigation in which it was being alleged by Church adversaries. When I was in the Church, I knew that litigants opposing the Church were constantly making fair game allegations against us and that those allegations were nonsense. I also know the frustration those allegations caused because of the willingness of courts and juries to embrace them. From my experience in litigating against the Church, I can see that nothing has changed in this regard. I also know from my experiences in suing the Church and from my association with other litigation adversaries of the Church that they know that "Fair Game" as they portray it is not Church policy. "Fair Game" exists only as a litigation tactic employed against the Church."
(Source: Declarations of V. Azanaran, 19th May 1994)
L. Ron Hubbard Affidavit 1976
"Fair Game Cancelled" Policy
"Fair Game" Comparisons to Other Religions
*This question has more information on the Scientology Myths Blog.