Earlier

[Volcano1985]

Anonymous had earlier issued a statement "warning" the Turkish government that it should stop its acts of Internet censorship which, according to the group, were "in violation of basic right and freedoms."

Should it be like one of two below?

Anonymous has earlier issued a statement "warning" the Turkish government that it should stop its acts of Internet censorship which, according to the group, are "in violation of basic right and freedoms."

Anonymous had earlier issued a statement "warning" the Turkish government that it should have stopped its acts of Internet censorship which, according to the group, were "in violation of basic right and freedoms."

[Mannysteps]

Not a teacherSince it is extending on the following, which is expressed in the past:
"Internet hacking and activist group Anonymous appeared unsuccessful in their initial online attack Thursday"

I think the best option is:

"Anonymous had earlier issued a statement "warning" the Turkish government that it should stop its acts of Internet censorship which, according to the group, were "in violation of basic right and freedoms."

If it was a refference to the something expressed in the present, like:

"The Turkish govermement is closing its circle on internet activists."

Then I'd opt for:

"Anonymous has earlier issued a statement "warning" the Turkish government that it should stop its acts of Internet censorship which, according to the group, are "in violation of basic right and freedoms."

The third option sounds strange because of the use of "warning" concerning something that has already happened. If instead "saying that", for instance, was used it would sound to me perfectly okay, although not a replacement for the first instance given:

"Anonymous had earlier issued a statement "saying that" the Turkish government should have stopped its acts of Internet censorship which, according to the group, were "in violation of basic right and freedoms."

An opinion I would like discuseed,
M.

[5jj]

Internet hacking and activist group Anonymous appeared unsuccessful in their initial online attack Thursday against Turkish institutions that condone Internet filtering as three of its members were arrested Friday in Spain.
Anonymous had earlier issued a statement "warning" the Turkish government that it should stop its acts of Internet censorship which, according to the group, were "in violation of basic right and freedoms."
Initial Anonymous attack on Turkish institutions fails - Hurriyet Daily News and Economic Review

The tenses are fine.

'They had earlier (than Thursday) issued a statement...'. Past Perfect - correct.


'...it should have stopped...' has a different meaning, namely that there was an ignored duty to stop at an earlier time.

'...it should stop...', now or in the future is correct.


'...which, according to the group, were...' is, implicitly, reported, and therefore 'were' is correct. As the situation still continues,, 'are' would also be acceptable. If the reporter had moved the inverted commas from after to before this word, only 'are' would have been correct.