Eligibility or legal readiness of the vessel embraces her conformity with all local regulations at the port of call, such as OPA 90 or USCG Regulations for example. It also encompasses custom, health and immigration clearances whichever is applicable. Unless expressly required by the contract, if preliminaries, such as free pratique, have not actually been granted will not prevent the tendering of a valid notice, as long as there is no reason to suppose that there will be any delay.
Per Lord Coleridge, CJ, in Smith v Dart & Son (1884) 14 QBD 105 at p.108:
A day was fixed on which the steamer should arrive free from pratique and ready to load and if the steamer did not arrive on that day the charterers were to have the option of cancelling the charter. The evidence is that the steamer did not arrive in the port of loading on the December 15th so as to be free from pratique on that day. She arrived on the 13th, but was not free of pratique on the 15th, that would be a ground which would give the charterers an option of cancelling, which they exercised. The question is whether the clause giving that option is independent stipulation, or whether it overrides the whole charterparty down to the point where the clause stands. I have come with regret and after some hesitation clearly to the conclusion that the stipulation does override the whole charter down to the place in which it is inserted, and on that ground, as the steamer did not arrive at the time prescribed, the charterers had a righ cancel, and as they did cancel the charter, the judgment was rightly entered and there should be no new trial.
Per Donaldson J in Shipping Developments Corp v V/O Sojuzneftexport (The Delian Spirit)  1 Q.B. 103 at p.115:
I should hold that a vessel is ready to load and can be an arrived ship if she is in such a state of physical and legal readiness that there is nothing to prevent her being made ready at once if required. This has been held by the Court of Appeal in relation to physical readiness in Armement Adolf Deppe v John Robinson & Co. Ltd.  2 K.B. 204. In that case it was pointed out that it was an idle exercise to take the hatch covers off whilst the ship was lying at a waiting berth, per Swinfen Eady LJ, at p. 208. I would go further and say that it was a breach of the shipowner’s duty to take care of the cargo. I see no reason why the same principle should not apply to free pratique. It is an idle exercise to obtain free pratique before the time for loading unless it be required for ship’s purposes, and if it is a fact that it can be obtained at any time and without the possibility of delaying the loading, the mere fact that it has not been obtained does not prevent the ship from becoming an arrived ship.
Per Longmore LJ in AET Inc Ltd v Arcadia Petroleum Ltd (The Eagle Valencia),  EWCA Civ 713 at paras2, 4, 16:
2. Strictly speaking a vessel will not be ready to load or discharge on arrival unless and until the port authorities have (inter alia) satisfied themselves that the vessel is free from infectious disease and that the crew are thus free to make contact with the shore; that means in the time-honoured phrase that the vessel has to be granted "free pratique".
4. Nowadays the granting of free pratique is likely to be something of a formality and the need for free pratique will not, at common law, prevent a notice of readiness from being given, see The Delian Spirit  1QB 103. But the parties can, of course, in their contract make other arrangements e.g. (as in Additional Clauses attached to Shellvoy 5) that time is to begin to run 6 hours after free pratique has been granted.
16. … free pratique is not an exam which one can fail. It is something which, …, is granted or not granted. If Owners apply for the grant of free pratique, it is hardly an abuse of language to say that the Owners "fail … free pratique" until it is granted.