Rule 15.3
The RD has overriding authority of the following matters....
e: The use of the safety car.
This is section 15 is full:
15) OFFICIALS
15.1 From among holders of an FIA Super Licence the following officials will be nominated by the FIA:
a) Three stewards one of whom will be appointed chairman.
b) A Race Director.
c) A Permanent Starter.
15.2 From among holders of an FIA Super Licence the following officials will be nominated by the ASN
and their names sent to the FIA at the same time as the application to organise the Event:
a) One steward from among the ASNs nationals.
b) The clerk of the course.
15.3 The clerk of the course shall work in permanent consultation with the Race Director. The Race
Director shall have overriding authority in the following matters and the clerk of the course may
give orders in respect of them only with his express agreement:
a) The control of practice, sprint qualifying session and the race, adherence to the timetable
and, if he deems it necessary, the making of any proposal to the stewards to modify the
timetable in accordance with the Code or Sporting Regulations.
b) The stopping of any car in accordance with the Code or Sporting Regulations.
c) The stopping of practice, suspension of a sprint qualifying session or suspension of the
race in accordance with the Sporting Regulations if he deems it unsafe to continue and
ensuring that the correct restart procedure is carried out.
d) The starting procedure.
e) The use of the safety car.
15.4 The stewards, the Race Director, the clerk of the course and the Technical Delegate must be
present at the start of the Event.
15.5 In exceptional circumstances, should any stewards not be present at the start of the Event, they
must be available and contactable at all times to fulfil their duties.
15.6 The Race Director must be in radio contact with the clerk of the course and the chairman of the
stewards at all times when cars are permitted to run on the track. Additionally, the clerk of the
course must be in race control and in radio contact with all marshal's posts during these times.
15.7 The stewards may use any video or electronic means to assist them in reaching a decision. The
stewards may overrule judges of fact.
15.3 isn't giving the Race Director
ultimate power it's setting out what the role of the Clerk of the Course is and where the limits of their role lie. It's frankly perverse to treat it as allowing the Race Director to override the rules set out elsewhere and it frankly says nothing good about Masi that he put forward such an argument or the stewards that they accepted them - although, to be fair, aren't really there to engage with this kind of legal shenanigans. I can't believe any court would give this interpretation the time of day although - of course - I am not a lawyer.
Even then, even if this rule does grant him the power, it was still wrong of him to use that power to deviate from the written rules and all established precedent. Legal does not mean justifiable.