ValidationRulesValidator.cs

using System;
using System.Runtime.Serialization;
using Sitecore.Common;
using Sitecore.Data.Items;
using Sitecore.Data.Validators;
using Sitecore.Rules;
using Sitecore.SecurityModel;
using MyProject.Foundation.Validation.Consts;
using MyProject.Foundation.Validation.Rules.Contexts;


namespace MyProject.Foundation.Validation.Validators.Fields.ValidationRules
{
    [Serializable]
    public class ValidationRulesValidator : StandardValidator
    {
        public ValidationRulesValidator(SerializationInfo info, StreamingContext context)
            : base(info, context)
        {
        }


        public ValidationRulesValidator()
        {
        }


        public override string Name
        {
            get { return "Validation Rules"; }
        }


        protected override ValidatorResult Evaluate()
        {
            var item = GetItem();
            var field = GetField();

            if (item == null || field == null)
            {
                return ValidatorResult.Valid;
            }

            Item rulesItem;

            using (new SecurityDisabler())
            {
                rulesItem = field.Database.GetItem(SitecoreIds.FieldValidationRules.ToID());
            }

            if (rulesItem == null)
            {
                return ValidatorResult.Valid;
            }

            var validatorsRuleContext = new FieldValidatorsRuleContext
            {
                Item = item,
                FieldValue = GetControlValidationValue(),
                FieldId = field.ID,
                Validator = this,
                Result = ValidatorResult.Valid,
                Text = string.Empty
            };

            var ruleContext = validatorsRuleContext;

            var rules = RuleFactory.GetRules<FieldValidatorsRuleContext>(rulesItem, "Rule");

            if (rules == null)
            {
                return ValidatorResult.Valid;
            }

            rules.RunFirstMatching(ruleContext);

            Text = GetText(ruleContext.Text);
            return ruleContext.Result == ValidatorResult.Valid ? ValidatorResult.Valid : GetFailedResult(ruleContext.Result);
        }


        protected override ValidatorResult GetMaxValidatorResult()
        {
            return GetFailedResult(ValidatorResult.Error);
        }
    }
}

Where are the "SitecoreIds" coming from?