The full statement from the FIA

Having studied the radio traffic between Vodafone McLaren Mercedes (McLaren) and its drivers, together with the FIA observer's report and data from the team, it is clear that McLaren's actions during the 2007 Monaco Grand Prix were entirely legitimate and no further action is necessary.

The facts

1. A two-stop strategy is the optimum at Monaco unless the safety car is deployed, in which case one-stop can sometimes be better.

2. The safety car has been deployed during four of the past five Monaco Grands Prix.

3. Under current rules the choice between a one-stop and two-stop strategy must be made before the final qualifying period.

4. It is clear from FIA measurements taken after qualifying that McLaren fuelled Hamilton for five more laps than Alonso.

5. This allowed Hamilton the option of a one-stop strategy should the safety car have come out during his first stint.

6. The safety car was not deployed.

7. The McLaren was significantly faster at Monaco than any other car.

Background

The primary objective of any team is for one of their drivers to win.  If this can be achieved they will try to ensure their other car finishes second.

With no safety car during Alonso's first stint, there was a small but finite risk that it would come out during the five laps before Hamilton had to refuel.  This would have put him behind the field and at a significant disadvantage to any car on a full (as opposed to optional) one-stop strategy.  The latter cars would be expected to refuel around lap 40 - ie after the safety car had pitted if it came out during Hamilton's extra laps.

For similar reasons Hamilton was called in early for his second pit stop, thus assuring his second place, with or without a safety car.

Had the car in front of Hamilton not been his teammate, McLaren might (probably would) have decided to risk the safety car and let Hamilton run for as long as his fuel load allowed in the hope that he would come out of the pits in the lead after one of his pit stops.  There is, however, no obligation on them to take this risk in order to overtake their own car.  Indeed it would be foolish to do so.

It is standard procedure for a team to tell its drivers to slow down when they have a substantial lead.  This is in order to minimise the risk of technical or other problems.  It is also standard practice and entirely reasonable to ask the drivers not to put each other at risk.
 
McLaren were able to pursue an optimum team strategy because they had a substantial advantage over all other cars.  They did nothing which could be described as interfering with the race result.