No need to speculate. Here's from the Official race rules:

ARTICLE 28
ANTI-DOPING CONTROL
A.S.O. and each of the teams participating believe it is absolutely necessary to
strictly respect the rules and recommendations set out by the competent authorities
in anti-doping as well to display totally irreproachable conduct in this
respect. The teams participating hereby undertake to apply the said rules and
recommendations and shall be solely responsible for ensuring that they are
respected by their team members and more generally by all their employees
and service providers.

The Tour de France is subject to the rules of the UCI and the Fédération Française
de Cyclisme (French cycling federation) concerning anti-doping control testing
designed to reveal the use by competitors of forbidden substances. For antidoping
control tests, the organisers have put in place a certain number of facilities
for competitors and the designated officials:

• Installation on each stage, next to the finishing line, of a mobile home
specially equipped for taking samples in the most comfortable and discrete
conditions.
• Transfer as soon as practicable, notably by private plane, of the samples
intended for the designated anti-doping test laboratories, in order to
speed up the analysis procedures and notification of results.
With regard to prizes, the results of a positive anti-doping control test are as
follows:
• Any competitor declared positive following a given stage shall forego all
earnings obtained during this stage.
• Any competitor disqualified from the race shall forego all earnings and
prizes acquired from the day of the control test in question.

ARTICLE 29
DISQUALIFICATION - EXCLUSION
29.1 A.S.O. believes it is vital to preserve its image and reputation, as well as
those of the event.
In compliance with article 2.2.010 bis lines 7 and 8 of the UCI governing cycling
sports, A.S.O. expressly reserves the right to refuse the participation in
– or disqualify from – the event, a team or one of its members whose presence
is liable to damage the image or reputation of A.S.O. or those of the event.
In case of disagreement with UCI and/or the team and/or one of its members
concerning the decisions thus taken by A.S.O., the dispute will be referred
to the Chambre Arbitrale du Sport (the French sports arbitration agency), Maison
du sport français, 1 avenue Pierre de Coubertin, 75640 Paris Cedex 13,
France.
29.2 Furthermore, A.S.O. may exclude from the event any team or any of its
members in the following cases:
• A breach of the event’s rules, including those concerning the event’s
internal discipline (rules concerning accommodation, for example).
• A serious breach of French law.
• Indecent appearance or inappropriate behaviour.
• Acts of vandalism performed during or outside the race.
• Failure to use the collective means of transport provided by the organisers
for transfers.
• Customs fraud, etc.

In case of disagreement with UCI and/ or the team and/or one of its members
concerning the decisions thus taken by A.S.O., the dispute will be referred
to the Chambre Arbitrale du Sport (the French sports arbitration agency), Maison
du sport français, 1 avenue Pierre de Coubertin, 75640 Paris Cedex 13,
France.