11 CFR 110.20(b) says that
A foreign national shall not, directly or indirectly, make a
contribution or a donation of money or other thing of value, or
expressly or impliedly promise to make a contribution or a donation,
in connection with any Federal, State, or local election.
In connection with this, the Federal Election Commission has expressed an opinion in this letter of 3 Dec. 2007 bearing on this topic
the Act and Commission regulations also provide that the term
“contribution” does not include “the value of services provided
without compensation by any individual who volunteers on behalf of a
candidate or political committee.” 2 U.S.C. 431(8)(B)(i); see also 11
CFR 100.74.
By contrast, if a foreign volunteer supplies "stuff" (a donut), that is a thing of value, as legally defined. This despite the fact that 100 hours of labor usually costs more than a donut. In another letter, 3 Aug. 1990 the FEC opined that paid information is a thing of value:
If, however, Mr. Hochberg imparts poll result information to you or
anyone else working for your campaign, including any data or any
analysis of the results, or if he uses the poll information to advise
your campaign on matters such as campaign strategy or creating media
messages, such poll information will constitute an in-kind
contribution from Mr. Hochberg to your campaign, and an expenditure in
an equal amount by your committee. 11 CFR 106.4(b)
The information to be provided was not just "something somebody knew", it was the paid results of a prior poll (by another candidate). The restriction only applies to information that was paid for.