The warrant bit is disengenous.

The NSA requires a warrant to evesdrop on your communications (content). They do not claim to need a warrant to include your data in a network graph so long as the “target” of the effort is related to foreign inteligence.

From the NYTimes story:

In the 2011 memo explaining the shift, N.S.A. analysts were told that they could trace the contacts of Americans as long as they cited a foreign intelligence justification. That could include anything from ties to terrorism, weapons proliferation or international drug smuggling to spying on conversations of foreign politicians, business figures or activists.

Analysts were warned to follow existing “minimization rules,” which prohibit the N.S.A. from sharing with other agencies names and other details of Americans whose communications are collected, unless they are necessary to understand foreign intelligence reports or there is evidence of a crime. The agency is required to obtain a warrant from the intelligence court to target a “U.S. person” — a citizen or legal resident — for actual eavesdropping.

So basically if the NSA targets Greenpeace in Germany, they are allowed to include all US-based Greenpeace activists in the analysis and are also allowed to distribute those activists information outside of the NSA if they find anything incriminating.

They just can’t listen to your phone calls or read your emails to do it (unless they get a warrant).