CRPD/C/GC/2 29. It is helpful to mainstream accessibility standards that prescribe various areas that have to be accessible, such as the physical environment in laws on construction and planning, transportation in laws on public aerial, railway, road and water transport, information and communication, and services open to the public. However, accessibility should be encompassed in general and specific laws on equal opportunities, equality and participation in the context of the prohibition of disability-based discrimination. Denial of access should be clearly defined as a prohibited act of discrimination. Persons with disabilities who have been denied access to the physical environment, transportation, information and communication, or services open to the public should have effective legal remedies at their disposal. When defining accessibility standards, States parties have to take into account the diversity of persons with disabilities and ensure that accessibility is provided to persons of any gender and of all ages and types of disability. Part of the task of encompassing the diversity of persons with disabilities in the provision of accessibility is recognizing that some persons with disabilities need human or animal assistance in order to enjoy full accessibility (such as personal assistance, sign language interpretation, tactile sign language interpretation or guide dogs). It must be stipulated, for example, that banning guide dogs from entering a particular building or open space would constitute a prohibited act of disability-based discrimination. 30. It is necessary to establish minimum standards for the accessibility of different services provided by public and private enterprises for persons with different types of impairments. Reference tools such as the ITU-T recommendation Telecommunications Accessibility Checklist for standardization activities (2006) and the Telecommunications accessibility guidelines for older persons and persons with disabilities (ITU-T recommendation F.790) should be mainstreamed whenever a new ICT-related standard is developed. That would allow the generalization of universal design in the development of standards. States parties should establish a legislative framework with specific, enforceable, time-bound benchmarks for monitoring and assessing the gradual modification and adjustment by private entities of their previously inaccessible services into accessible ones. States parties should also ensure that all newly procured goods and services are fully accessible for persons with disabilities. Minimum standards must be developed in close consultation with persons with disabilities and their representative organizations, in accordance with article 4, paragraph 3, of the Convention. The standards can also be developed in collaboration with other States parties and international organizations and agencies through international cooperation, in accordance with article 32 of the Convention. States parties are encouraged to join ITU study groups in the radiocommunication, standardization and development sectors of the Union, which actively work at mainstreaming accessibility in the development of international telecommunications and ICT standards and at raising industry’s and governments’ awareness of the need to increase access to ICT for persons with disabilities. Such cooperation can be useful in developing and promoting international standards that contribute to the interoperability of goods and services. In the field of communication-related services, States parties must ensure at least a minimum quality of services, especially for the relatively new types of services, such as personal assistance, sign language interpretation and tactile signing, aiming at their standardization. 31. When reviewing their accessibility legislation, States parties must consider and, where necessary, amend their laws to prohibit discrimination on the basis of disability. As a minimum, the following situations in which lack of accessibility has prevented a person with disabilities from accessing a service or facility open to the public should be considered as prohibited acts of disability-based discrimination: (a) Where the service or facility was established after relevant accessibility standards were introduced; 9